Peter T. Thomas

Examination of immune parameters and host resistance mechanisms in B6C3F1 mice following adult exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin

Adult female B6C3F1 mice were given a single ip dose of 0, 01, 1.0, or 10.0 micrograms/kg 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and examined for immune function and host resistance 7-10 d later. Exposure to TCDD resulted in a significant dose-related decrease in induction of both IgM and IgG antibody-forming cells. This suppression was noted for both T-dependent and T-independent antigens. TCDD at a dosage of 10 micrograms/kg was shown to suppress production of antibody to viral hemagglutinin. In contrast, TCDD exposure had no significant effect on natural killer cell function, production of interferon, or various parameters of macrophage function. Assessment of host resistance revealed a significant increase in susceptibility to fatal infection with influenza virus, but no significant alteration in susceptibility to infection with the bacterium Listeria monocytogenes.

Effects of morphine tolerance and abstinence on cellular immune function

Female B6C3F1 mice were rendered tolerant-dependent on morphine by a combination of injections and pellet implantation. Mice were injected with morphine sulfate (20 mg/kg, s.c.) twice a day on day 1. On day 2, they were implanted s.c. with a 75 mg morphine pellet for 3 days. On day 5, the pellets were either left intact (tolerant) or removed 8 h prior (abstinent) to carrying out the immune function tests. A high degree of tolerance to the analgesic and hypothermic effect of morphine developed as a result of this procedure. Similarly, physical dependence also developed as evidenced by the signs of the abrupt and naltrexone-precipitated abstinence syndrome. Implantation with morphine pellets resulted in a profound, statistically significant reduction in spleen and thymus weight and cellularities, with the greatest degree of reduction noted in abstinent animals. Morphine tolerance was associated with suppressed B-cell proliferation following in vitro stimulation, as well as interleukin-2 (IL-2) and interleukin-4 production by T-cells. NK cell activity was significantly reduced in morphine-tolerant, but not in morphine-abstinent, mice following a 24 h incubation in the presence or absence of IL-2. In comparison, the in vitro induction of cytotoxic T-cells was significantly depressed in morphine-abstinent, but not morphine-tolerant, animals. Exposure to morphine apparently had limited effect on macrophage function as assessed by production of tumor necrosis factor. These studies demonstrate a differential effect on immune effector and regulatory mechanisms in morphine tolerance and abstinence processes.

Comparison of Immune Functional Parameters Following In Vitro Exposure to Natural and Synthetic Amphetamines

The potential of synthetic and natural amphetamines to modulate cellular immune effector and regulatory mechanisms was evaluated in an in vitro exposure system. Murine splenic lymphocytes and elicited peritoneal macrophages were cultured with 0.0001-100 microM of amphetamine sulfate, methamphetamine hydrochloride, or the (S) or (R) isomers of cathione hydrochloride. T-lymphocyte regulatory function was assessed by quantitating the production of cytokines, and T-lymphocyte effector function was assessed by the induction of cytotoxic T-lymphocytes (CTL). B-lymphocyte function was measured by proliferation, and natural immunity was assessed by quantitating basal and IL-2 augmented natural killer (NK) cell activity. None of the compounds tested had any direct effect on cellular viability. Exposure to amphetamine resulted in a significant suppression of IL-2, but not IL-4, production by T-lymphocytes, as well as a suppression of B-lymphocyte proliferation only at the highest amphetamine concentration examined. NK cell function was slightly suppressed by amphetamine exposure, but was enhanced by methamphetamine exposure. Conversely, exposure to either (S) or (R) isomers of cathinone resulted in stimulation of IL-2 production, B-lymphocyte proliferation, and CTL induction. No significant effect of cathione was noted on NK cell function. These data suggest that natural and synthetic amphetamines exhibit differential immunomodulatory activity following in vitro exposure.

Immunomodulatory Effects of in vitro Exposure to Morphine and Its Metabolites

Both in vivo and in vitro exposure to morphine have been reported to produce a number of immunomodulatory effects in both laboratory animals and humans. The current study was performed to assess the direct in vitro effect of exposure to morphine or morphine metabolites on immune response parameters. Murine B6C3F1 splenic lymphocytes or peritoneal macrophages were cultured in vitro at concentrations of 0.0001-100 mumol/l morphine sulfate, morphine-3-glucuronide, morphine-6-glucuronide, or normorphine. B cell proliferation was significantly suppressed following exposure to all drugs. Production of interleukin (IL)-2, IL-4, and IL-6 was affected only moderately by all drugs except morphine-6-glucuronide, which produced a marked suppression at 100 mumol/l. Both basal and augmented natural killer (NK) cell function were unaffected by any drug except morphine-6-glucuronide, which enhanced NK cell activity at concentrations between 0.0001 and 1.0 mumol/l. In contrast, both morphine-3-glucuronide and morphine-6-glucuronide significantly inhibited cytotoxic T lymphocyte induction at concentrations between 0.0001 and 100 mumol/l, whereas morphine and normorphine were inactive in this assay. In summary, in the absence of direct cellular cytotoxicity, a differential immunomodulation was observed following in vitro exposure to morphine and its metabolites.

Effects of subchronic exposure to a mixture of O3, SO2, and (NH4)2SO4 on host defenses of mice

Mice exposed 5 h/d, 5 d/wk up to 103 d, to 0.2 mg O3/m3 or to a mixture of O3, 13.2 mg SO2/m3, and 1.04 mg (NH4)2SO4 aerosol/m3 showed significantly greater susceptibility to group C streptococcal aerosol infection relative to filtered air controls. Pulmonary bactericidal activity by alveolar macrophages was significantly enhanced in the lungs of mice exposed to the mixture relative to those inhaling filtered air or O3 alone. The total number and distribution of the free cells lavaged from the lungs, as well as cellular ATP levels, did not change due to the pollutant exposures. In vitro cytostasis in tumor target cells cocultured with peritoneal macrophages from the exposed mice was significantly enhanced in the O3-exposed and in the mixture-exposed treatment groups relative to controls and also in the mixture-exposed relative to the O3-exposed group when a target-to-effector-cell ratio of 1:10 was used; no such effects were observed when this ratio was 1:20. Splenic T-lymphocyte function, as measured by blastogenesis to mitogens and alloantigens, was affected by exposure to O3 and/or the mixture, although the patterns of effects were qualitatively different. Splenic B-cell function and macrophage antigen processing, as measured by the generation of antibody plaque-forming cells, was unaffected by exposure.

A comparative study of immunomodulation produced by in vitro exposure to delta opioid receptor agonist peptides

The present study assessed the direct immunomodulatory effect of a panel of synthetic peptides exhibiting delta-opioid receptor agonist activity. Murine splenic lymphocytes and peritoneal macrophages were cultured in vitro with peptides at concentrations of 0.00001-10 microM. Assessment was made of B-cell function by quantitating cellular proliferation, T-cell function by measuring cytokine production, natural immunity by quantitating basal and cytokine-augmented natural killer (NK) cell activity, and macrophage function by production of IL-6. These peptides had minimal effects on B-cell proliferation at any concentration examined. In comparison, enhancement of cytokine production by T-helper cells occurred following exposure to several of the compounds, to a significant extent with DPDPE, DPDPE-trifluoroacetate, or deltorphin-1 and most pronounced at concentrations between 0.00001 and 0.1 microM. Likewise, IL-6 production by macrophages was significantly augmented by exposure to these three peptides. NK cell function was significantly enhanced by in vitro exposure to several of the peptides, with enhancement generally noted at concentrations between 0.00001 and 0.01 microM. However, some of the peptides (most notably DADLE) greatly suppressed NK cell activity. These data suggest that delta opioid agonists are broadly immunomostimulatory.

Evaluation of host resistance and immune function in cadmium-exposed mice☆

Adult female B6C3F1 mice received distilled water only or water containing 10, 50, or 250 ppm of cadmium chloride (CdCl2) for 90 days. Body weights were measured weekly. On selected days during exposure and on Day 91, Cd tissue concentrations were measured along with changes in primary antibody responses. On Day 91 mice also received a primary challenge with various infectious agents. T- and B-cell mitogenesis, natural killer (NK) cell function, delayed type hypersensitivity (DTH) as well as macrophage bactericidal activity, and phagocytosis were measured. There was no change in body weight gain, organ weights, or in humoral immunity during treatment even though cadmium had accumulated in significant quantities in the tissues. Compared with controls, exposure to cadmium had no statistically significant effect on mortality and mean survival time following primary or secondary challenge with any of the infectious agents. However, there was a dose-related, increased susceptibility to Herpes simplex type 2 virus. T- and B-lymphocyte proliferation was significantly reduced, and macrophage phagocytosis was significantly increased following cadmium exposure. NK cell activity was augmented, but not significantly. Macrophage bactericidal activity and DTH were not significantly altered.

Suppression of immune function by non-peptidic delta opioid receptor antagonists

Previous studies in this laboratory and elsewhere have provided evidence that compounds acting as delta opioid receptor agonists exhibit marked immunostimulatory potential. Conversely, the delta opioid receptor antagonists have previously been shown to demonstrate immunosuppressive effects as assessed by proliferation of T-cells following allogeneic or xenogeneic stimulation. The present study was performed to further characterize this immunosuppressive activity using the compounds benzylidene naltrexone (BNTX), naltrindole (NTI), and naltriben (NTB). In vitro exposure to BNTX resulted in an apparent dose-related suppression of B-cell proliferation, cytokine production by T-helper cells, and natural killer (NK) cell activity, with statistically significant suppression observed at concentrations between 1 and 10 microM. NTI was also immunosuppressive for all immune function parameters examined, although this compound was less active than BNTX. In vitro exposure to the structurally related compound NTB had no significant effect on any immune function examined in this study. In all cases, immunosuppression occurred in the absence of any detectable alteration in cellular viability, suggesting a specific immunosuppressive effect rather than overt toxicity.

Direct cellular immunomodulation produced by diacetylmorphine (heroin) or methadone.

1. Abuse of the narcotic drug diacetylmorphine (heroin), as well as methadone, a drug for treating heroin addiction, has been associated with alterations in immune function in humans. The current study was performed to assess the direct (in vitro) immunomodulatory effect of exposure to these drugs, in view of the very limited studies reported thus far on this effect. 2. Murine splenocytes or peritoneal macrophages were cultured in vitro at concentrations of 0.0001-100 microM heroin or methadone. B-cell function was assessed by quantitating cellular proliferation in response to stimulation with an antigen analog; T-cell regulatory function was assessed by culturing splenocytes with or without drugs in the presence of anti-CD3 antibody and subsequently quantitating cytokine production; and T-cell effector function was evaluated by culturing lymphocytes with or without drugs during a 5-day induction culture followed by assessment of specific cytotoxic T-lymphocyte (CTL) activity. Natural immunity was assessed by quantitating basal and IL-2 augmented natural killer (NK) cell function, and macrophage function was assessed by cytokine production. 3. In vitro exposure to heroin resulted in decreased B-cell proliferation at concentrations of 1-100 microM, and methadone had a similar effect at concentrations of 0.1-100 microM. 4. Production of IL-2 was suppressed by 0.1-100 microM of heroin, whereas exposure to methadone appeared to result in a generalized modulation, with suppression of IL-2 at most concentrations. In contrast, IL-4 production was only affected at the 100 microM concentration of both drugs.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of host resistance and immunity in mice exposed to the carbamate pesticide aldicarb.

Adult female Swiss-Webster and B6C3F1 mice received distilled water only or water containing 0.1, 1.0, 10, 100, or 1000 ppb of aldicarb daily for 34 days. The target concentration of aldicarb present in the 10 ppb dosing solution was analytically verified on a daily basis as was its stability over a 48-hr period. To develop an immune profile of this compound, functional parameters measured after exposure included resistance to infectious viral challenge; quantitation of splenic antibody-forming cells to sheep erythrocytes and circulating serum antibody levels; splenic lymphocyte blastogenesis to T- and B-cell mitogens; and mixed-lymphocyte culture response. To supplement the functional assays, complete blood counts, differential leukocyte counts, and body and relative organ weights were measured. In addition, gross and histopathologic examinations of tissues relevant to the immune system were performed. The absence of significant effects on any of these parameters suggests that aldicarb at environmentally relevant exposure concentrations is not immunotoxic in rodents.